diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 1ad6109..7b346a1 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -6217,8 +6217,23 @@
   if (!DstTy.isVector())
     return UnableToLegalize;
 
-  if (MaskTy.getSizeInBits() != Op1Ty.getSizeInBits())
+  // Vector selects can have a scalar predicate. If so, splat into a vector and
+  // finish for later legalization attempts to try again.
+  if (MaskTy.isScalar()) {
+    Register MaskElt = MaskReg;
+    if (MaskTy.getSizeInBits() < DstTy.getScalarSizeInBits())
+      MaskElt = MIRBuilder.buildSExt(DstTy.getElementType(), MaskElt).getReg(0);
+    // Generate a vector splat idiom to be pattern matched later.
+    auto ShufSplat = MIRBuilder.buildShuffleSplat(DstTy, MaskElt);
+    Observer.changingInstr(MI);
+    MI.getOperand(1).setReg(ShufSplat.getReg(0));
+    Observer.changedInstr(MI);
+    return Legalized;
+  }
+
+  if (MaskTy.getSizeInBits() != Op1Ty.getSizeInBits()) {
     return UnableToLegalize;
+  }
 
   auto NotMask = MIRBuilder.buildNot(MaskTy, MaskReg);
   auto NewOp1 = MIRBuilder.buildAnd(MaskTy, Op1Reg, MaskReg);